The present invention relates to an electronic timepiece and, more particularly, to an automatic correction system of a reference signal frequency in an electronic timepiece.
In general a quartz oscillator is employed in an electronic timepiece for developing a reference signal of a predetermined frequency, for example, one hertz via an appropriate frequency divider. The oscillation frequency of the quartz oscillator is usually adjusted through the use of a variable capacitor called a trimmer. However, the natural frequency of the quartz oscillator will undergo modification with the lapse of time in an irreversible manner on account of the phenomenon of "ageing" and on account of the environment, for example, the ambient temperature and any shocks to which the oscillator is subject.
Heretofore, it has been proposed, to eliminate the above deficiencies, to provide an oscillation frequency stabilizing circuit or a temperature compensation circuit in an oscillation circuit for driving the quartz oscillator. However, these circuits operate in an analogue fashion and require large spaces in an electronic timepiece. Therefore, these circuits can not be employed in, especially, an electronic wristwatch.
Recently, a zero adjustment system has been developed in which the zero adjustment of second information in an electronic timepiece is carried out upon receiving a command from the operator through a zero adjust switch. In such a system, the time information is nearly corrected to show accurate time information when the zero adjust operation is commanded in response to a time tone. But the tendency in gaining or losing of the electronic timepiece can not be compensated.